It is desirable to efficiently lock parts together with a minimum of effort. The fewer the number of steps involved, the quicker assembly can be accomplished.
There are several existing systems for locking parts together. One system is shown in U.S. Pat. No. 3,167,336 to E. F. Lewis issued Jan. 26, 1965. In this patent a pair of barbs are used to wedge a male member in a female member. The barbs precede a recess that aids the wedging process. Because the barbs bend into their associated recess, it is externally difficult to remove the male member from the female member.
Another such assembly is disclosed in U.S. Pat. No. 3,730,109 to Kreizel et al issued May 1, 1973. In this assembly a leg is locked to a table by sliding a spline in a complimentary tapered recess. Once in place one end of the spline rests against a shoulder in the recess.
The '336 patent depends upon wedging action rather than locking action to connect the male member to the female members. The wedged connection can be separated if enough separation force is applied to the male member. The action is dependent on deflection of the barbs to wedge the male member into the female member and to separate the male member from the female member.
The '109 patent shows engagement of splines in a complimentary recess without discussing how the connection is accomplished.